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Evolution and Natural Selection

Evolution and Natural Selection. Chapter 5 Pages 96-102. PREMISES OF EVOLUTION. Process by which populations of organisms change over time All modern species arose from earlier forms. Evolutionary history is like a branching tree of life . All life began as first prokaryotes existing 4.

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Evolution and Natural Selection

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  1. Evolution and Natural Selection Chapter 5 Pages 96-102

  2. PREMISES OF EVOLUTION • Process by which populations of organisms change over time • All modern species arose from earlier forms. • Evolutionary history is like a branching tree of life. • All life began as first prokaryotes existing 4

  3. Charles Darwin and “On the Origin of Species by Means of Natural Selection” (1859) • In 1831 he sailed on the H.M.S. Beagle -All species have common ancestor -Primary mechanism is natural selection

  4. Darwin Voyage • Before Darwin geologists were finding that the earth was much older than previously thought • Discovered from fossils and rocks • Charles Lyell- proposed that the physical features of the earth, such as mountains and valleys were formed over a long period of time.

  5. Charles Darwin (1809-1882)

  6. Voyage of the HMS Beagle 1831-1836

  7. Charles Lyell (1797-1875)

  8. Geological Change • First- if geological change is slow and continuous, then the earth must be very old. • Second- slow and subtle changes that occur over centuries and millennia can produce substantial changes. • As Darwin sailed around the world he was amazed by the DIVERSITY of life.

  9. Thomas Malthus (1766 - 1832)

  10. Formulation a Theory for Evolution • Thomas Malthus- observed that the human population was continuing to grow and, if unchecked, would eventually run out of space and food • If this were true of humans, who have relatively few offspring, it must be even more true of plants and animals that produce numerous offspring.

  11. Evolution by natural selection • Darwin contemplated his thoughts for many years • Until 1858, when he read a paper by Alfred Russell Wallace • This encouraged his to come forward with his view

  12. Wallace • Working in Malaysia • Formulating his own theory of natural section and evolutions • Similar to Darwins

  13. 1859 • Charles Darwin was to first to come forward with his published book • On the Origin of Species by Means of Natural Selection

  14. 1859- Darwin Publishes On the Origin of Species by Means of Natural Selection On the same year Alfred Wallace also publishes about natural selection

  15. Evolution by Natural Selection • Developed in 1858 • Individuals compete for limited environmental resources • Artificial Selection- which is practiced by farmers • Only animals and plants with certain desirable traits are selected for breeding in an effort to produce more animals or plants with the same traits. • Darwin believed the same process occurred in nature • Natural Selection • A process that favors the survival and reproduction of those organisms that possess variations best suited to their environment.

  16. Cont. • Unlike artificial selection natural selections acts without the purpose of a farmer or breeder • Selecting for those best able to survive and reproduce under the environmental conditions in which they live

  17. Selective Forces • Physical and biological characteristics of the environment • Selection occurs over many generations • Organisms become better adapted by the process that can involve all aspects of an organism, such as anatomy, physiology, and behavior.

  18. Survival of the “fittest” • An adaptation is a trait that increases the fitness of an individual. • Fitness is the contribution an individual makes to the next generation, relative to the contribution of others. • Evolution by natural selection occurs when a population of organisms changes (adapts) over time as a result of individuals with heritable traits leaving more offspring than other individuals.

  19. Darwin’s four premises • 1. All organisms produce more offspring than can possibly survive to reproduce • 2. there is a great deal of variation of traits among individuals in natural population. Many of these variations can be inherited.

  20. 3. the amount of resources necessary for survival is limited. Therefore organisms must complete with each other. • Organisms that inherit traits that make them better adapted to their enviro. Are more successful in the competitions for resources. They are more likely to reproduce, and pass on these traits.

  21. Genes and Natural Selection • Modern discoveries in the fields of genetics and molecular biology have not contradicted Darwin’s theory but have expanded and deepened our understanding • The modern synthetic theory of evolution is essentially Darwins idea as it has been refined by modern genetics.

  22. Asexual Reproduction • Offspring receive their genes from only one parent, and as a result, they are identical to the parent in all of their characteristics (clones) • The only source of variation is MUTATION • Efficient because mating is not necessary.

  23. Sexual Reproduction • Chromosomes from two parents are combined when specialized cells called SEX CELLS, or GAMETES unite during FERTILIZATION • Eukaryotic organisms normally contains two copies of each of the organisms' different chromosomes • DIPLOID

  24. Population Genetics • Environmental factors are not static but always changing • Pop. Must adapt to survive and reproduce • An organism’s biological success, or FITNESS, is measured by the number of its own genes present in the next generation.

  25. New Species Evolve • New species evolve from existing species • Each different kind of organism is a different species

  26. Typological Definition of Species • In the past a species was defined as an organism with a definable set of characteristics that is visibly different from other similar organisms. • Example- two organisms of the same size and shape but a different color may be considered a dif. Species. • Typological • Based on the morphology, or the structure and appearance of the organism.

  27. Type Specimen • For the purpose of identification, a museum specimen considered to be a representative of the species is designated the Type Specimen and other specimens are then compared to the type

  28. NOT IDEAL • This is not always the best way. • Many species look different because of sex or age. • Top Female Razorfish • Bottom Male Razorfish • Sexual Dimorphism

  29. More Diversity • Top Juvenile Bluehead Wrasse • Bottom Adult Bluehead Wrasse

  30. Reproductive Isolation • Means the members of different species are not in the same place at the same time or are physically incapable of breeding

  31. Habitat Isolation • Due to habitat two species are never able to breed because they will never encounter each other • Ex. • If one species of snail lives on sandy beaches in the Caribbean, and a similar species lives in mangrove swamps.

  32. Anatomical Isolation • Copulatory organs that prevent similar species from reproducing with each other

  33. Behavioral Isolation • Some animals exhibit special behaviors during the breeding season, and only members of the same species recognize the behavior as courtship. • Male Cuttlefish display a striped pattern

  34. Temporal Isolation • If the time that members of one species are ready to reproduce does not coincide with the time members of a related species is reproducing

  35. Biochemical Isolation • Offspring because biochemical or genetic differences between their gametes prevent successful fertilization • When fertilization does occur it can result in an infertile offspring • Hybrid • Mule

  36. Process of Speciation Speciation- refers to the various mechanisms by which new species arise Begins with two or more populations of the same species becoming geographically isolated from each other.

  37. Allopatric Speciation • Responsible for the greatest bumber of species. • Changes such as- Earthquakes, mountain building, and the formation of islands can separate populations • First step in evolution.

  38. The creationist viewpoint... • all species have independent creation • species do not evolve through time • the age of species is young (~6 Ky)

  39. The Lamarckian viewpoint... • all species have independent origin, i.e., not related by descent • species evolve through time

  40. Comparing the Creationist and Lamarckian viewpoints... 6000 years ago Millions of years ago

  41. The Darwinian viewpoint... Common ancestor to pine and wheat Common ancestor to dog and wolf Common ancestor to all species • all species are related by descent, i.e., share a common ancestor • species evolve through time

  42. What evidence do we have to support evolution by natural selection? i.e., what evidence exists that supports the hypotheses that species evolve through time and are related by descent? 1) Direct evidence

  43. Artificial selection

  44. http://medlem.spray.se/birdsongs/div.%20billeder/billeder/drengene.jpghttp://medlem.spray.se/birdsongs/div.%20billeder/billeder/drengene.jpg

  45. Natural selection in action: beak evolution in one of Darwin’s finches

  46. Why insecticides fail Fig. 22.12

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